Identified from email image by Dr. Rob Cannings, who stated "When young, Blue Dasher adults are brown with yellowish stripes on the abdomen and sides of thorax, but males become bluish with maturity.... Lives in marshy ponds and lakes in lowlands. Pretty common on the south coast, espcially on the islands, although still on the Blue List. One Interior locality at Osoyoos Lake. In Canada mainly in southern Ontario and extreme southern BC, but abundant and common over most of US."
This dragonfly was found in a house on a white windowsill, which shows the colour on the wings to advantage.